The Sleep Cycle...What Happens?

Reading this past chapter in my psychology textbook, I found the section about the sleep cycle intriguing. I pondered about the different stages of sleep, and what happens in each stage. The sleep cycle is divided into two main categories: REM sleep and NREM sleep. REM is an acronym for "rapid eye movement" and NREM stands for "non-rapid eye movement. Each of these categories have unique psychological and neurological features. NREM sleep actually consists of three stages. During stage one, the alpha waves in the brain power down from a frequency of 8-13 Hz to a frequency of 4-7Hz. This is the stage where people also experience random twitches or feelings as if they are falling into space. Conscious awareness of the external environment fades away. In stage two, brain waves referred to as sleep spindles operate at 11-16 Hz. During this stage conscious awareness disappears, and almost half of an adult's sleep is spent in stage two of NREM sleep. In stage three, delta waves only range from .5-2 Hz. This stage can be characterized by night terrors that children and few adults can experience. Finally, after the three stages of NREM, do we fall into REM sleep. REM sleep can account for 20-25% of an adult's sleep cycle. In REM sleep, we experience the most wild and vivid dreams. In REM, our eyes move frequently and dart around. One hypothesis is that this could be due to the fact the human eye is trying to make sense out of what we are "seeing" in dreams. Throughout the night, humans cycle in and out of REM sleep. So there you have it, a brief summary of one of the human body's most important functions.